1. Field of the Invention
This invention relates to a cruising control apparatus which is used for running an automotive vehicle at an arbitrarily preselected speed and possible to automatically control running speed of the vehicle at the desirably selected cruising speed without operating the accelerator pedal of the vehicle.
2. Description of the Prior Art
For example, an apparatus provided with following functions has been known as a cruising control apparatus for automatically control running speed of the vehicle at the desirable target speed.
In the conventional cruising control apparatus, a set switch disposed in a switch panel of the apparatus is operated by a driver when the running speed of the vehicle attains desired speed suitable for the automatic constant speed cruising while the vehicle is travelling, thereby storing a vehicle speed signal detected by a speed sensor at the time of off-operation of the set switch in a memory housed in a controller as a target cruising speed. Whereby, constant speed cruising control is started, the controller in the apparatus always compares the actual vehicle speed signal generated from the speed sensor with the speed signal stored in the memory as the target cruising speed, executes control calculation according to the difference therebetween and controls the vehicle speed so as to harmonize the actual vehicle speed signal with the stored speed signal by driving the throttle valve of the vehicle in the opening or closing direction through an actuator. Accordingly, the vehicle cruise automatically at the objective constant speed.
When the brake pedal is operated during the aforementioned cruising control, the cruising control is cancelled without clearing the speed signal stored in the memory according to the off-operation of the set switch, and the automatic cruising is switched over to the ordinary running according to the accelerator pedal operation by the driver.
After this, when a resume switch disposed in the switch panel is operated, control is done so as to return the vehicle speed to the target cruising speed previously stored in the memory of the controller, whereby the cruising control at the constant speed is restarted similarly to the control before the brake operation after the vehicle speed returns to the target cruising speed.
When an acceleration switch is operated during the cruising control, the vehicle speed begins to increase. If the switch is switched off when the vehicle speed increases up to the desirable speed, the vehicle speed signal generated from the speed sensor at the time of off-operation of the acceleration switch is stored in the memory as a new target cruising speed and the cruising control is started directing the newly stored vehicle speed at the time of off-operation.
Contrary to the above, when a coast switch in the switch panel is operated during the cruising control, the vehicle speed begins to decrease. If the coast switch is switched off when the vehicle speed decreases down to the desirable speed, the vehicle speed signal generated from the speed sensor at the time of off-operation of the coast switch is stored in the memory as a new target cruising speed, whereby the cruising control is started directing the newly stored vehicle speed at the time of off operation.
Furthermore, when a tap-up switch is operated during the cruising control, a speed signal obtained by adding a predetermined signal corresponding to a tap-up speed to the speed signal stored in the memory or the actual vehicle speed signal generated form the speed sensor at the time of operating the switch is stored in the memory in the controller, and the cruising control is started at a speed higher than the target speed or the actual vehicle speed at the time of operating the tap-up switch by the predetermined tap-up speed (for example, 1.6 km/h).
When a tap-down switch in the switch panel is operated during the cruising control, a speed signal obtained by subtracting a predetermined signal corresponding to a tap-down speed from the speed signal stored in the memory or the actual vehicle speed signal generated form the speed sensor at the time of operating the switch is stored in the memory in the controller, and the cruising control is started at a speed lower than the target speed or the actual vehicle speed at the time of operating the tap-down switch by the predetermined tap-down speed (for example, 1.6 km/h).
There has also been a cruising control apparatus provided with an acceleration switch and an coast switch which serve also as the tap-up switch and the tap-down switch, respectively.
In such the apparatus, when the acceleration switch is operated during the cruising control, the vehicle speed data at the time of switching on the acceleration switch is subtracted from the vehicle speed data at the time of switching off the acceleration switch and obtained fluctuation in the vehicle speed is compared with a predetermined constant value. The signal generated from the acceleration switch is decided to be a tap-up command in a case the fluctuation in the vehicle speed is less than the predetermined constant, and is decided to be an acceleration command in a case the fluctuation is not less than the predetermined constant.
When the coast switch is operated during the cruising control, the vehicle speed data at the time of switching off the coast switch is subtracted from the vehicle speed data at the time of switching on the coast switch and obtained fluctuation in the vehicle speed is compared with a predetermined constant value. When the fluctuation of the vehicle speed is less than the predetermined constant, the signal generated from the coast switch is decided to be a tap-down command, and if the fluctuation of the vehicle speed is not less than the predetermined constant, the signal is decided to be a coast command.
Furthermore, a cruising control apparatus has been also known, which is further provided with a shift-down demand signal generator for generating a shift-down demand signal to the transmission controller of the vehicle at the time when the actual vehicle speed falls below the target cruising speed stored in the memory of the controller and a difference between the actual vehicle speed and the target speed exceeds the predetermined value on an uphill road, for example. The transmission controller is so designed as to slow down the automatic transmission of the vehicle in response to the shift-down demand signal after recognizing the vehicle speed, the position of the select lever, the opening degree of the throttle valve and so on.
However, in the cruising control apparatus with the acceleration switch and the coast switch used also as the tap-up switch and the tap-down switch in common, there is a problem in that acceleration control is started unexpectedly without executing tap-up control in a case where the acceleration switch is operated repeatingly in a short time and the second operation is done similarly to the first operation of the acceleration switch during the cruising control, and coast control is started unexpectedly without executing tap-down control in a case where the coat switch is operated repeatingly in a short time and the second operation of the switch is done similarly to the first operation of the coast switch during the cruising control.
In the cruising control apparatus with the function to shift down the automatic transmission at the time when the actual vehicle speed falls below the target cruising speed more than the predetermined difference in the speed by generating the shift-down demand signal, it is so designed that generation of the shift-down demand signal may be delayed for a certain fixed amount of time in each of cases where the set switch is operated while the cruising control is not performed, the resume switch is operated while the cruising control is cancelled, and the acceleration switch is operated during the cruising control, accordingly there is a problem in that the shift-down of the transmission is not always carried out even in a case of necessity, and the driver and passengers sometimes feel a sense of incompatibility in a case where the shift-down of the transmission is performed after the certain amount of time.
Also in the cruising control apparatus of the above-mentioned type, the controller is also designed so as to interrupt the decision of the output of the shift-down demand signal for a certain amount of time similtaneously to on-operation of the acceleration switch if the acceleration switch is operated on at the time when the actual vehicle speed begins to increase in a case where the vehicle is cruising automatically under the cruising control in a state that the transmission controller shifts down the automatic transmission of the vehicle in response to the shift down demand signal. Therefore, the generation of the shift-down demand signal is interrupted for the certain amount of time, and there is another problem in that the automatic transmission may be shifted up automatically during the interruption of the signal.
Furthermore, generally in the cruising control apparatus, when the tap-up command or the tap-down command signal, the controller of the apparatus is so designed as to drive the actuator in the acceleration or deceleration direction of the vehicle by outputting a tap-up initialize signal or a tap-down initialize signal every time of generation of the command signals in response to the respective command signals.
The tap-up initialize signal is calculated by the controller in accordance with the cruising speed at the time of generation of the tap-up command signal and outputted in an amount suitable for increasing the vehicle sped as much as the predetermined tap-up speed (for example, 1.6 km/h) against the cruising speed at the time of constant speed cruising under the cruising control, and the tap-down initialize signal is similarly calculated by the controller in accordance with the cruising speed at the time of generation of the tap-down command signal and outputted in an amount suitable for decreasing the vehicle speed as much as the predetermined tap-down speed (for example, 1.6 km/h) for the cruising speed at the time of constant speed cruising under the cruising control. Therefore, if the tap-up command signal is generated successively by operating the switch repeatedly, the tap-up initialize signal, which is calculated by the controller on condition that the vehicle speed is increased in the constant cruising state, is outputted continuously in response to the second and successive operation of the switch in the state where the vehicle speed begins to increase according to the operation in the first time, consequently there is a problem in that the vehicle is accelerated over the target cruising speed renewed in response to the tap-up command signal. There is also the similar problem in that the vehicle is decelerated under the target cruising speed renewed in response to the tap-down command signal owing to the continuation of the output of the tap-down initialize signal when the tap-down command signal is generated successively by the continuous operation of the switch.
In addition to the above, the actuator in the apparatus is so designed as to be fixed in a short period of time after the generation of the tap-up initialize signal or the tap-down initialize signal, so that the output of the tap-up or the tap-down initialize signal is merely output and the feed-back control against the target cruising speed is not executed substantially in a case where the tap-up command signal or the tap-down command signal is repeatedly generated in a certain interval. Accordingly, there is another problem in that the difference between actual vehicle speed and the target cruising speed becomes larger more and more, and it becomes impossible to speedily conform the actual vehicle speed with the target cruising speed at a time when the tap-up or the tap-down command signal is repeated in special timing.
Furthermore, when the tap-up command signal is generated many times successively, the tap-up speed (for example, 1.6 km/h) is added one after the other to the target speed stored in the memory of the controller for each generation of the signal and the target cruising speed increases continuously. Consequently, the difference between the actual vehicle speed and the target cruising speed becomes larger and sometimes exceeds the predetermined difference range (for example, 5 km/h). The vehicle speed control by the controller is so designed as to be switched over from constant speed control (feed-back control aiming the target speed stored in the memory) to constant acceleration control in order to speedily conform the actual vehicle speed with the target speed by maintaining the acceleration of the vehicle constant at the time when the actual vehicle speed falls below the speed lower than the target speed stored in the memory of the controller by the predetermined difference range.
If the tap-up command signal is generated even after the vehicle speed control is shifted to the constant acceleration control, the tap-up initialize signal is output in response to the command signal in addition to the actuator driving signal according to the constant acceleration control, therefore there is a problem in that pleasant driving feeling may be obstructed by abrupt acceleration of the vehicle at every switching operation.
Also in the conventional cruising control apparatus in a type of renewing the target speed stored in the memory with the vehicle speed obtained by subtracting the predetermined tap-down speed form the actual vehicle speed in response to the tap-down command signal, if the tap-down command signal generated at the time when the actual vehicle speed falls below the speed lower than the target speed stored in the memory by the predetermined range (for example, 5 km/h) and the constant acceleration control is performed as described above, the speed signal corresponding to the vehicle speed lower than the present vehicle speed by the predetermined tap-down speed (for example, 1.6 km/h) is stored in the memory of the controller as a new target cruising speed and the constant speed cruising at the speed lower than the present vehicle speed is started after discontinuing the constant acceleration control to conform the actual vehicle speed with the target cruising speed higher than the present vehicle speed.
Namely, the vehicle speed control is suddenly changed into the constant speed cruising control aiming the speed lower than the present vehicle speed at the time of generation of the tap-down command signal from the constant acceleration control aiming the speed higher than the present vehicle speed by at least 5 km/h, for example. Therefore, there is a problem in that overshooting of the vehicle speed occurs after the switching operation and comfortable driving feelings bay be spoiled.
Further, in the conventional cruising control apparatus, the controller is designed so as to drive the actuator in the acceleration direction of the vehicle by outputting a set initialize signal calculated by using a data map, which is preset for starting the cruising control in response to the cruise command signal, as a coast initialize signal in a case where the coast command signal disappears and the vehicle speed control is shifted from deceleration state according to the coast control into the constant speed cruising in the vehicle speed at the time of disappearance of the coast command signal. Accordingly, there is a problem in that the coast initialize signal is sometimes output excessively according to difference of the duration time of the coast command signal and it becomes impossible to speedily conform the actual vehicle speed with the newly stored target cruising speed in response to the coast command signal.